Methods and apparatus for the control of the timing of recurrent signals



Feb- 19, 1952 A. D. BLUMLEIN ETAI. 2,586,605

METHODS AND APPARATUS FOR THE CONTROL oF THE TIMING 0F RECURRENT SIGNALS original Filed Jan. 11, 194e 2 SHEETS- SHEET 1 `/rc. Pff/asf am, CMA/65K Humm!lHllllmmtmmImmun Feb- 19, 1952 A. D, BLUMLl-:IN ET AL 2,586,605

METHODS AND APPARATUS FOR THE CONTROL v OF THE TIMING OF' RECURRENT SIGNALS Original Filed Jan. l1, 1946 2 SHEETS- SHEET 2 0l ,D A 50a Kc. P//Asf f 1 il?. d?

Patented Feb. 19, 1952 UNIT-eo ,1s-rares METHODS AND APPARATUSFORJ-'IHE (JON--v i TRQLI OF THE LTIMING. LOE REQURRENITI;

A SIGrNALS;

Alan Dower' Blumlein, deceased; late" of`Lodon,

" England; by Doreen Walkerfexefcutrix, Tit-ign-V ton,-Engla-nd, and Erie LawrenceCasling White', Iver, Englandfassignors to: .ElectriciiMusicaL 2 Industries Limited, a British company Originalv application. .Tanuary' 11i m46;I Serial No.

' 640596. Divi'ded' and ithis applicationApril'SU;

1949sC Serial No'."90,724. InGreatflrit'aix IDe Y v Thisfi application '-is a division .cfa application Serial-No640,596,` led January 111,. 1946,' inthe I-IamesvofflA.v D'. Blumleinl. and L. vC...,White, and?k entitled: .Improvements .inor v.R.e1at.ingr..to Methods and Apparatus#for thelControl oftthe Timing of Recurrent...Signalsi Thisiinvention.- .relates :.to apparatus lfor,` the. controlvof 1 theiI timing lofv recurrent. signals;Y

.' Methods: are,.already-A known by:` which :.the.

phase .of 1 electrical;4 signalslsmay zbe adjusted,for. 10;v

example, by. rotatingtlthey moving coil on asgoniometer of: kvvhichv the `two` xed..ipairs ot coils .i are', fedsfwith thel signal insquadrature. "In:suclfnar-v rangements; the phase Jofssignalsfobtained. `from the moi/ing I coil of the;` goniometerzy Will be: de-l termined Aby:thenangular: position.. of this coil. Although: the angularl position .of .thel coil may bef accuratelyf measured. by 1 gearing thefmotion. of'rithef coil. toan..indicating.. devices trainsi-.oi gearing-have fbacklash1-which-.zlimitthe nal accuracy-robtainable.V Further, iv the s phaseofrlthe signals maynot be directlyzproportional toithe angular position -oftha coill due.: to` .imperfections..A inl-the goniometer. Such.zmethods: .therefore require apparatushofvery carefulndesign and: :construction to i enable theu phase` vof 1 'the signals tocbe adjnstedwith4 accuracy. Itwisan `object.' of this invention touprovide, improved apparalnis` of,y relatively simple :design and .constructionI for.` the: accuratefcon-trol of,v thewtiming` ofi` recurrent electrical pulses.

'lBroadly,; accordingA to the: present; invention, apparatus for generating-.aseries of f electricalv pulsesmf. i adjustable timing includes means: pro-- vvidingfza plurality .of seriesoff'signals, the-sig*- nals: .inf eachr seriesl being-recurrent at*I ai frequency which is an integral multplesoftheifre-- quency of, the signals in the .next series of lower frequency and having a.durationwhich is shorter tl'larrfthatl ofA the signals insaid' nextfseries;v the: lowest frequencybeing thatiof the pulses whichl itsis desired-to generate,ineansarranged to gencrate-:lan outputipulsev onlywhen signals/from eachfof said-iSeries are simultaneously.applied` quency -sof'that f the K' timing of Y theJv generated I Y J2 pulses mayw-beaadlusted; to; then: samen accuray '1 as,l that` of said signals orhighestrequenclsi .In the. case inlwhich .twacscries ofsignals are, employed', apparatussaccording lto.,ithe zinven:

ries,loi-,signalsrecurreniaat;` aazfrequencyf .fnmeansfor controlling the timing of said seriesiofasigf, nelsai second source.. Droxliding: L ay second i series or signalsgrof; shortensduratione and; recnr-.. rent-Aat at'fnequencyfnf; where; ngisaiztnsinteger.-l meansgfior; controllingathe .timing .ofi` salda-secrA ond seriesfofesignals; a.-;device.= arranged-:to genf` erate an output.pulsesonlyfWhemsignalsaofssaid first; anctifsecondaseriesaarezafeda to: dtisilnultaneouslycfsaidnrst; anda'-seconclz-controllingimeans;

being,4 ,sminten-fonnected that; ,emersa-ming signal, of-saidasecondnseriesissalwaysz-zfediato; saidgidevice; during.T aisignalr ofmtheiirstfserieszcwheref; by. ithegntiminggof; the; generatednpulses;isideterminedifby. -thegftimi'ng-fo saimsecondsseries of;

signals i-sofxthatsthe;timingsof ithe:generatedk pulses may be adjusted to the-.:sameaccuracy. 'as-saidA seconds seriesnof :.signals.,

Pref erablyazwhere three:.-series 'yofisignalsaare employed Jappaeratus.:accordings to them'nveirtion comprisescassnurceeproyidingr `a.tl'iirdiseriesnof signals; of Ish-orten; durationathanasaid':secnndase:` riesnf signals andirecurrent at.caavfrequencyV wherexmg; isfian.:'ntegeri.7 means.;orffclonf`A 3m trolling the timing ofcsaid; thirdfseries ofxsignals,

as; secnndi deviceaarrangedzzto: provideianoutputl onlyfmhen the4 output-:fromm:saidrrstfmentinnecl device and saidithirdiseriesr..ofzfnignalsilaraed; tot; it Qrsirnultanenusljr, ssaidfzithird.: controlling i; meansbeingintencnnnectedawitlnzsaid tstaand seeondacnntrollingimeans; sthaneveryvzntlt "sig-i nalsofcsaid; tlcirihseries occurs' during assignali oiisaid'f-zsecondsvseries,` whereby: @the :timingnof they generatednpuzlsesn: maynbey adiustedcto :the:

samelziaenuraey'asi thegtiming: oasaidathirdase videithe signalsrofntrequency j: orfnfsandlj; rei-z spectiyelm s 1- iln-y particular; dormsi,.nf-zapparatus@embodying thegiinventionnthe :fmeansffforv Arcontrolling` #theI timingoofgithes seriesmf.i signalsincludesv an -anw gularly@adjustableV element. sozarranged @thatilt-hej timing-.'ofs'said :signals lineanlmrelated ytoifthe angular;:rotationiy ofasaidilelement .i anduone: `f" saidaielement's- `-is coupledt another ot'fsaidfelements'wwh'ich controls theiftiiningfoffa sez'iesfoff 5.5i signals:fof'klcwerffrequency by reduction gearing of predetermined ratio, so that vwhen said elements areadiustedr a; signal of the series of higher frequency always occurs during a signalA of the series of lower frequency. Particular forms of means for controlling the timing of the signals may consist of Vone or;,more gonicontrol the timing at which the sawtooth A. wave-1 form causes the valve to conduct to produce an output.

The means arranged to generate anoutputv pulse or the device or second device to which the separate series of signals are applied may consist of a thermionic valve having two control electrodes to each of which a series of signaisv of different frequency .is fed, said valve being so arranged .as only to give an output when signals areV simultaneously applied to both of said grids.-

l In .order that the invention may be more clearly understood and readilly carried into effect,..alternative forms of pulse ltiming circuit arrangements Will-now be described in greater detail by way lof example with reference to the accompanying drawings, in which:

I Figure 1 shows a general schematic circuit diagram of an arrangement for the accurate control of the timing of pulses by means of goniometers,

Figure 2 shows a circuit diagram of an alternative pulse generator of adjustable timing, and Figure 3 shows a block and circuitdiagram of an embodiment of the invention that includes the circuit of Figure 2 for the accurate control of the timing of pulses.

In the several gures similar parts are indicated by similar reference characters.

Referring to Figure 1, it will be seen that the circuit comprises a valve V, from the anode circuit of which recurrent pulses are obtained, and the goniometers GN1, GN2 which control the timing of these pulses by controlling the timing of a first series of pulses of frequency and the Second series of pulses of frequency nf derived from the oscillators O2 and 01,'respectively, in a manner which will hereinafter be described.

It will be assumed that the oscillator O1 is an oscillator generating sinusoidal oscillations at 50,000 cycles/sec. The output from the oscillator Oris fed to one pair of coils of the goniometer GN1 and is also fed via a phase-changing device P1 of known type which rotates the phase of the oscillations by 90A to the other pair of coils of the goniometer GN1. The output from the moving coil of GN1 is fed to the limiting device L1, which converts the sinusoidal Voscillations into an oscillation of substantially rectangular waveform L1 and may conveniently 'take the form of a ythermionic valve amplifier adjusted in well Vknown manner to limit both positive and negative amplitudes of the applied oscillations. The output from L1 is applied to the diierentiating network D1 of known type, which may, for example, comprise a condenser inv series `with a resistance, which converts the limited sinusoidal oscillations into a series of sharp impulses of relatively short duration. These impulses may be utilized directly', or may be fed to a, pulse generator PG1,

4 which may be a multivibrator of knownvtype. to cause it to generate pulsesof short duration at the frequency of the oscillator O1, these pulses of short duration being the second series of pulses of frequency nf referred to above. The pulses thus generated by the pulse generator PG1 are fed in the positive sense to the grid G1 of the hexode valve V over an A. C. coupling comprising a condenser C1 and leak R1 the grid G1 being biasedv beyond anode current cut-off except when a pulse from the pulse generator PG1 is applied thereto.

The oscillations from the oscillator O1 are also fed via a, limiter L and a differentiating network D similar to the limiter L1 and the differentiating network D1. respectively, to a frequency divider FD of known type, which may be of the kind described in British Patent Specification No. 471,731. The frequency divider FD is arranged to deliver pulses of a frequency of le of that of the oscillator O1, namely, 5000 cycles/sec. and these pulses are applied to control a device O2, which may be a tuned circuit ora band-pass filter, so as to provide a sinusoidal output having afrequency of 5000 cycles/sec.

The sinusoidal oscillations from the device Oz are then treated in the manner which has previously been described with reference to the oscillator O1. They are fed in quadrature to thecoils of the goniometer GNz, and the output from the moving coil of this goniometer isfed via the limiter L2 andthe differentiatingynetwork D2 which corresponds to the limiter L1 and the differentiating network D1 to the pulse generator PGz and thence to the control electrode G2 of the valve V over the grid condenser C2 and its associated leak R2. The pulse generator PG1. is, however, arranged to provide pulses longer in duration'than those provided by the pulse generator PG1 and these pulses constitute the first series of pulses of frequency f referred to above. The control grid G2 is arranged to be normally biased beyond anode current cut-od so that the Valve V can only pass current when pulses from the pulse generator PGz are present.

The valve V is provided with two further electrodes which are connected to steady positive potentials so as to enable them to serve as screening electrodes, and its anode circuit is provided with an output load R. In operation, it is arranged that a voltage is set up across the load R only when pulses are simultaneously present on the control electrodes G1 and Gz, and the voltages thus set up constitute the series of pulses the timing of which is to be controlled and may be fed to a utilization circuit through a blocking condenser C. Y

The fixed coilsof the goniometers GN1 and GNz are adjusted so that whenever a pulse from the pulse generator PGz is applied to the control electrode G2, a pulse from the pulse generator PG1 is also .applied to the control electrode G1 at approximately the mean or average timing of the pulser from the pulse generator PGz. The duration of the pulse from the pulse generator PGe is arranged to be nearly equal to the time interval between successive pulses from the pulse generator PG1,A so that the maximum error in timing of the pulses from the pulse generator PGz may be tolerated whilst still ensuring that these pulses shall coincide in a particular case only with every 10th pulse from the pulse generator PG1. The output from the anode circuit of the valve V will therefore be a series of pulses having the duration o f theV pulses from the pulsewgenerator PG1 but recurrent atthe'ifrequencyofithe pulsesieomithe.

pulse generator PGz.

- The-adjustmentwof therti'ming `off'l theA pulses-in the-outputwcircuit' of ther-valve :Vtwill Anowibe descri-bed. AThisadjustment` isgefectedzbyirritating multaneously rotatingtheAL moving: coil: of: the

goniometer GNe-so as to maintainrthe'ftiming of.'

toa ensure fithatinov-Yslipping"ffcarr occur; f d'ue-:to a pulse other thans-every# successi-Ve .puise :selected I from the pulses-providedby-ythepulse'generator Y inithepa-rticularf ease-under consideration may conveniently-belidriven fromjthe moving-scenici thegoniometer i (Z1=l-\Tr=byJ al 10i: 1v reduction.E gearing indicated-kv atvl GRf; and -in=` viewf. of the relatively lair-ge""permissibley tolerance-.inthe timingof Ythe pulses derived from the goniometerGN, ltiwill bevv appreciatedf--tl'iatg this@ gearing need. :notube highly laccurfateV but `may .i he:v relatively cheap,y

Which doesVV not requirev precision gearing or goniometer'srof highly accurate design.

'The method which has-.been described may be applied two or more times so as to gather further increased accuracy of timing adjustment. Thus,

if the frequency .off the required.pulses-isi.5000v cycles/sec. an oscillator having la frequency of 500,000 cycles/sec. may be provided, and successively-.divided `to give' oscillations at Yfrequencies of 50,000 cycles/sec; and 5,000cycles/sec., respecangular movement. of of.the; moving coilpofy the goniometer fed Withzthe 50,000 cycles/sec.- oscillationwhich in turn causesan angularmove.- mentof 1- of the moving coil of the thirdggoniometer. The outputs fromv the moving coils of the rst two goniometers are then treated'inthe same manner as that described alcover with reference to the goniometersGNl and GN2, andthe output from a heXode valvecorresponding to the valve. Vis then fed via anamplifying valverwhich reverses its polarity, to one of the controlcelectrodes o1" another hexode. valve similarly. arranged,ato the other control electrode of which the pulses derivedfrom the third goniometer are applied after passing through further devices correspondingto the limiter L1, the diierentiating: network D1 and the pulse generator PG1. The pulses derived from 'theeoutputacircuit' of this further heXode '.will thus have `the duration of thehighest frequency. pulses, but will recur A- 5 f. creased approximately; '1,00 times.'-

therfaicnuracyrswithf@which theirggtirningfmayir be: adjusteds'will .ebe the? accuracy: Wthw which? the highesti. frequency: fpulseszmay; zbeeadjusted; JI-ln` otheriwords; theiaccuracy of :timing .has been fin Ther `inductive-i goniometersgl whichnhavea ibeen. refernedwto a in.; the precedingdescription;` :ma-jc be replaced: byecapacityo goniometerswfoknown type havingf two pairszofiixed,z platesarranged 'inxthe i close.: .au circular,` i outputs electrode. .screeningy v electrode -isslarranged to:rotate;..bei'vveen-..` :saidi circulan.- electrode) an'dwsaidepairs: ofiaxeda `plates s0f.as..vto;vary the direct' capacityfbetweenseachY. `g zpair .ci fixed plates-sand@said:circular: fplate, ,andi theophase of :the signals derived'vfromzsaidcfcir-l. cular electrode sis when,` determined; by;=the= 'angular positionnel ofnsaid screening: electrode; .l i n 1 '.Alternatiuelyusaidgoniometers may loereplacect` f -sbyrtime1delay networks-giving delay equalito 4the periodic time: offthes pulses ofmvhich: thea timing Y, is toebe s adjusted. =Such1 networks' are preferably., Y foldedi or loopedasoasxtoJoringl theirends adjacents. each'othen. and areziterminated'.sov as. to prevent` f zliyrefle'ctions` The; timingnoiithe,:pulses.,isz:adj usted lay-#rotating an arm. carrying anpickzup-electrode. soLLthat fit'v either ymakes fcontact:Y or hascapacity` to. diierentzpointsuinutthe lnetwork" :in turn.- folding the .networhso'las tmake fit otfsubstan.- waltially': circular' form=.and tobring; .its-.endsV adja-vr cent toaeach other; thepickl-S-up electrode'mayu-be A rotated .beyond' 360eandiithefitiming of the i pulses made proportionalitosthei angularrotation. of the arm-carryingithe. pick-.mp1. electrode. Itztl'i'efirfre-A rquency othe"v pulses is sufficiently :high tto.l permit eapaxzitative zpick-uppa second: time-delay net-rA Work similar to that which has been described may. berlset :upvs as. tothe rotatablewith refer-4 encefzto 1it;-so athatlany.` 'givenspointiinzsthe second!A .40e delay-netwo'rklisi:cap'acitativelycoupledaxvitlr suc-A cessive points inlthes :rstizf'delay :networleftas: thev two networks are rotated with. respect toweach other. ".Theitirning of the pulses delivered at ftheV I ends ofi- .th'ei second-'1 delay 'network :wi-115- theirg de.

pendiiupontthe relativeangularoposition offvithe timelnetworksf and 'm'aylloe Vcontinuously adjusted if byrotating:the-twoinetworkslwith'respect v toie'a'ch the'lej l "It-willf-beappreciatedthatfitixis-iunnecessary to i60 employ sinusoidal oscillations when time;'delayU networks arevfused instead' of:v goni'ometers; since theforrner are suitable forcontrollingtl'ieftinfia ingoi pulsesr'whereas thei latter can` onlyv be :used: satisfactorily Withwsinusoidal oscillations. "Thus, iff-time:delaynetworks-.arei used, .the limitersrandi differentiating; networks Lf,.D",-L1lD1,f etc.; are notlrequired; and theoscillators QusxOzeetc.; takeA thecformfofpulse generators; Y

A further alternativeto the'above-mentioned goniometersand. .timedelayf networks.willY new loe; described, ,withi reference- ,to Figure 2f, ,ofvv ,the e accompanying f, drawings. l.The t pulsev .generator PGr supplies .ther pulses, the. Qtimingof vwhich to' be contr'c'illed,` r.toltlie control VelectrodeA bffthe.. valve V1 over ah condenser ,C1 and leakRi;4 which j are. arranged so thatithegrid'current drawn' byther pulses biases the valve Vr; beyond anode currentcut-oit except: whenv pulses are present; TheJ valve VV1 is f thus' normallyi -nont:ondu'cting,` To but is rendered conductive'- whenever'apulse v is`v` applied toits controle electrode! AvThe anode/cath4 odepathfof @the valve V1i is connected in parallel with-the v condenserl .C'zp .Which 'isz c'onnecteda` iin Y series with yresistance fRz `acrosse; source.l ofzyolt-,

at the lowest, frequency, ,ie e.; ocycles/fsec.: anch-1;l ai. age; as t shown. ;;.Gnrrent :owsilfromzthis sourcei-l of voltage through the resistance R2 to charge the condenser C2 until the valve V1 is rendered conductive by a pulse from the pulse generator PG, when the condenser C2 is discharged through the valve V1. On the termination of the pulse from the pulse generator PG the valve V1 becomes non-conducting and the condenser. again commences to charge and so the cycle repeats itself. The voltage setup across the condenser Cz is thus of approximately saw-tooth form and has a frequency equal to that of the pulses from the pulse generator PG. The voltage set up across the condenser C2 is applied to the control electrode of a valve V2, which has a resistance R3 in its anode circuit and a resistancev R4 in its cathode circuit. A further valve V3 also shares the cathode resistance R1 and has a resistance R5 in its anode circuit. The control electrode of V3 is connected to a sliding contact on a potentiometer P connected in series with a fixed resistance Re across a source of voltage as shown. As previously indicated, the angularly adjustable member (the sliding contact on potentiometer P) serves to control a bias potential which is applied to the valve V2 to which the sawtooth wave form is applied so as tocontrol the timing at which the sawtooth wave form causes the valve V2 to conduct to produce an output. As the voltage across the condenser C2 increases, assuming this voltage has reached a value suiiicient to make both valves V2 and Vs conducting, the current in the anode circuit of both valves V2 and V3 will change, the current in the valve V2 will increase and the current in the valve V3 will decrease. When the condenser C2 is discharged by the valve V1, an opposite change in these currents will take place. By feeding the voltage set up across either the resistance Ra or R5 to a differentiating network, a series of pulses may be obtained having the same frequency as the pulses delivered by the pulse generator PG but having a timing dependent upon the position of the slider of the potentiometer P. The pulses thus derived from the resistance Ra or R5 may control a further pulse generator giving pulses of any desired duration and may then be applied to one of the control electrodes of a hexode mixer of the type described with reference to Figure 1 of the accompanying drawings.

As illustrated in Figure 3, in order to enable the timing of the pulses derived from the arrangement shown in Figure 2 to be controlled simultaneously with that of other pulse generators the slider of the potentiometer P may be mechanically coupled either to the sliders of other potentiometers controlling the other pulse generators or to the moving coil of a goniometer or to the rrotating pick-up element of'a time delay network. As the condenser Cz will charge exponentially, the potentiometer Pjis preferably given an` exponential law so that the timing of the pulses may have a linear relation to the movement of the slider of this potentiometer. Alternatively, the condenser C2 may be arranged to charge linearly by connecting a large choke in series with the resistance R2 in which case the potentiometer may have a linear law. Generally speaking, the pulse generator shown in Figure 2 is convenient for the low frequency pulse, and goniometers or time delay networks are more suitable for ,the higher frequency pulses, the timing of which hasito `be capable of contnuous adjustment through many cycles, thus timing adjustment.

In Figure 3, there is shown, .by Way of example,

three geared phase shifting circuits, one beingl of the goniometer type and the other two being of the type shown in Figure 2. The greater part of the circuit corresponding to that of Figure 2 is shown enclosed by a broken line rectangle iii. The capacitor IB and resistor I2 differentiate the sawtooth wave taken off the anode of the valve V2 to obtain a rectangular Wave that is applied to a suitable pulse generator I3. The generator I3 is triggered by the front edge of the rectangular wave to produce pulses having a suitable width or duration and having a tim-ql ing determined by said front edge. Y l

If desired, a second circuit of the type shown in Figure 2 may be included in the system as indicated by the block I0'. The circuit elements or units associated with the block I0 correspond to those associated with block I0 and are provided with the same reference charactersl with a prime added.

The valve V functions the same as valve V and has the output pulses of valve V applied to grid G1 by way of a polarity reversing valve l I5. The pulses from pulse generator I3' are applied to the grid G2.

What is claimed is: Y

l. In combination, a sine Awave oscillator, a chain of frequency divider units connected to divide the frequency of said oscillator output, said divider units being of the type that produces a pulse output, means for converting said pulse .outputs to sawtooth wave outputs, a plurality of ipping tubes to which said sawtooth Wave outv puts, respectively, are supplied, variable bias means for changing the clipping level of said clipping tubes, means for diiferentiating the outlput pulses of said clipping tubes whereby pulses are produced that are delayed with respect to the output pulses of said divider units as a function of said clipping levels, means for gearing said variable bias means together and for connecting them to a driving means whereby the clipping levels of said clipping tubes are changed simultaneously when said driving means is operated, the gear ratios between successive variable bias means being proportional to the frequency of the outputs of the divider units supplying signal to the clipping tubes controlled by said several variable bias means, respectively, and a pulse selector to which said delayed pulses are supplied.

2. In combination, a master oscillator, a chain of frequency divider units connected to divide the frequency of said oscillator output, said divider units being of the type that produces a pulse output, means for converting said pulse outputs to sawtooth wave outputs, a plurality of clipping tubes to which said sawtooth Wave outputs, respectively, are supplied, variable bias means for changing the clipping level of said clipping tubes over a range from substantially the top of said sawtooth wave to substantially the bottom of said sawtooth wave, means for differentiating the output pulses of said clipping tubes whereby pulses are produced that are delayed with respect to the output pulses of said divider units as a function of said clipping levels, means for ygearing said variable bias means together and for connecting them'to a driving means whereby the clipping levels of said clipping tubes are changed simultaneously when said driving means is operated, said gear ratios corresponding to the amount of frequency division in the corresponding divider f units, :fandia puls'euselector to :which said delayed lpulses are supplied. f

A.frequency divider unitv v"connected 1.to r":divide the Afor gearing said goniometerphase shifter and said lvariable Lbias ymean'sftogether whereby the 'clipping level of said .clipping Stube is @changed 'simultaneously with a .change in adjustment ofuf20 said goniometer phase shifter, the gear ratio of said gearing means being thc same as the amount of frequency division by said divider unit, and a pulse selector circuit to which the delayed pulses from said differentiating means and the signal from said goniometer phase shifter are supplied.

4. In combination, a sine wave oscillator, means including a frequency divider unit connected to divide the frequency of said oscillator output and to produce a pulse output, means for converting said pulse output to a sawtooth wave output, a clipping tube to which said sawtooth wave output is supplied, variable bias means for changing the clipping level of said clipping tube, means for differentiating the output pulses of said clipping tube whereby pulses are produced that are delayed with respect to the output pulses of said divider unit as a function of said clipping level,

a goniometer type phase shifter to which signal from said oscillator is supplied, means for gearing said goniometer phase shifter and said variable bias means together whereby the clipping level of said clipping tube is changed simultaneously with a change in adjustment of said goniometer phase shifter, the gear ratio of said gearing means being the same as the amount of frequency division by said divider unit, and a pulse selector circuit to which the delayed pulses from said differentiating means and the signal from said goniometer phase shifter are supplied.

5. In combination, a master oscillator, a chain of frequency dividers connected to divide the frequency of said oscillator output, said chain of dividers comprising at least a first frequency divider unit and a second frequency divider unit, sawtooth wave generators to which the output pulses of said divider units, respectively, are applied for causing said generators to produce sawtooth waves, clipping circuits to which the outputs of said generators, respectively, are applied, each of said clipping circuits including a variable clipping level control means for changing the level at which said sawtooth waves are clipped, means for adjusting the clipping level control means of said clipping circuits simultane- 6.5 ously and at a rate proportional to the repetition rates of the waves applied to said clipping circuits, and means for deriving pulses from the outputs of said clipping circuits which pulses are delayed as a function of said clipping level.

6. En combination, a master oscillator, a chain of frequency dividers connected to divide the frequency of said oscillator output, said chain of dividers comprising at least a first frequency divider unit and a second frequency divider unit,

"sawtooth wave generators to which ther output `pulsesof saidfdivider; units,- respectivelyL are applied forcausing said lgenerators-to produce clipped, rneans'for. adjusting fthe"y clipping level controlf means-'of said A`clipping circuits simultaneously and"atzthe-rate proportional lto the yrepetition ratesfof the waves applied tosaid clippingcircuits,- -means for derivinggpulses from the outputs'of4 saidi clipping circuits ywhich pulses arefdelayed as a function' of'isaid 'clipping level, and-fa pulse selector `to rwhich? said delayed, pulses `and'.output-signal: from-^said-master voscillator are applied.-

7. Apparatus forV generating a seriesof electrical pulses tof adjustable v4timing, `includingxa iirst'zsource :providing 'a rsti-gseries of signals recurrent at a frequency f, means for controlling the timing of said series of signals, a second source providing a second series of signals of shorter duration and recurrent at a frequency nf, where 1i is an integer, means for controlling the timing of said second series of signals, a device arranged to generate an output pulse only when signals of said first and second series are fed to it simultaneously, said rst and second controlling means being so inter-connected that every nth signal of said second series is always fed to said device during a signal of the rst series, whereby the timing of the generated pulses is determined by the timing of said second series of signals so that the timing of the generated pulses may be adjusted to the same accuracy as that of said second series of signals, and wherein each of said means for controlling the timing of said series of signals includes an angularly adjustable element so arranged that the timing of said signals is linearly related to the angular rotation of said element and one of said elements is coupled to another of said elements, which controls the timing of a series of signals of lower frequency by reduction gearing of predetermined ratio, so that when said elements are adjusted a signal of the series of higher frequency always occurs during a signal of the series of lower frequency, and wherein at least one of said means for controlling the timing of said signals includes a sawtooth voltage waveform generator, the frequency of which is controlled by pulses and a valve to which said sawtooth waveform is applied, and means including an angularly adjustable member controlling an adjustable bias potential which is applied to said valve so as to control the timing at which said sawtooth waveform causes said valve to conduct and so to produce an output.

8. In combination, means for producing a sawtooth wave, a pair of vacuum tubes each having a cathode, a grid and an anode, an anode voltage supply, means for applying said sawtooth wave to the grid of the first one of said tubes, a cathode resistor common to said cathodes and through which said cathodes are connected to the low voltage end of said anode voltage supply, an anode resistor for the rst one of said tubes through which the high voltage end of said supply is connected to the anode of said one tube, said high voltage end also being connected to the anode of the other tube, means for taking a sawtooth wave output off the anode end of said anode resistor, means for applying a bias voltage to the grid of the second one of said tubes, means for varying'said bias whereby the starting time of said output sawtooth wave is varied, and a differentiating circuit toA which said output sawtooth wave is applied whereby there is obtained a rectangular wave having a front edge that has a timing determined by the value of said bias.

9. In combination, means for producing a sawtooth wave, a first vacuum tube and a second vacuum tube each having a cathode, a grid and an anode, an anode voltage supply, means for applying said sawtooth wave to the grid of said first tube, a cathode resistor common to said cathodes and through which said cathodes are connected to the low voltage end of said anode voltage supply, an anode resistor for one of said tubes through which the high voltage end of said supply is connected to the anode of said one tube, said high voltage end also being connected to the anode of the other tube,v means for taking a sawtooth wave output of! the anode of said one tube, means for applying a bias voltage to the grid of rsaid second tube, and means for varying said bias whereby the starting time REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,419,546 Grieg Apr. 29,1947 2,422,205 Meacham June 17, 1947 2,466,044 Schoenfeld Apr. 5, 1949 2,471,268 Gaines May 24, 1949 

